What Causes Irregular And Heavy Bleeding?

hello, i am 16 and had sex two weeks ago whilst i was on my period. After that i had to go to the toilet often and somethimes leaked a bit of blood but not much. Today i started bleeding heavily and some blood clots escaped. I went to the toilet again just now and no blood came out anymore my urine looked clean what is this? could it be a small miscarriage or just an infection! My parents are in Holland at the moment so i cant go to the doctors because i live in spain and i dont speak spanish what should i do?